Fluids when not properly contained can be destructive. Such destructiveness can be of immense scale or minute. For example, on the larger scale, rivers can flood, destroy property and injure people. Toxic liquid chemical spills can destroy items the spills come in contact with. On the smaller scale, fluids such as water, entering into electronic equipment such as radios, computer terminals can cause short circuiting of electrical wiring and even create electrical shock potential for users. On an intermediate scale, fluids and spills can affect building structures.
Modern semiconductor fabrication facilities utilize sophisticated technical manufacturing equipment, materials and chemicals such as acids and other fluids, and processing mechanisms such as pipes, feed systems and sinks, and are operated by personnel who work in various locations within the facilities. Many such facilities include multi-level building constructions with floors and ceilings separating upper and lower level vertically aligned rooms and work areas.
One critical aspect of a semiconductor fabrication facility is the necessity for a "clean room" environment, such that during manufacture the microscopic semiconductor "chips" do not become contaminated with foreign particles. Such clean rooms are designed such that circulated air flow is maintained uniform so that such particles are convected by air away from the chip products being manufactured. To accomplish such air flow, clean room floors are typically constructed with patterns of holes to allow air to flow from upper to lower levels in a constant "down flow" manner with a goal that the structures will avoid causing eddies, turbulence or other air flow interference.
Safety professionals in companies who have semiconductor fabrication facilities with such down flow configurations are concerned with safety matters regarding such open style floors and potential spills and leaks, particularly those involving toxic or corrosive chemicals typically used in the semiconductor fabrication process, which could penetrate the flooring used in such facilities. Injuries to personnel and damage to equipment can occur as a result of such leak or spill penetrations. For example, leaking sinks of acid could fall on expensive high voltage electrical equipment or come into physical contact with personnel who may be in the lower area. These spill problems can result in multi-million dollar costs to a semiconductor manufacturer if not effectively and efficiently addressed. Clean-up and replacement of damaged equipment can be costly. Product delays can result in lost profits. Injuries to personnel can be severe.
Therefore, a need exists for efficient cost effective spill containment while at the same time maintaining the uniform airflow needed in such facilities. Various prior approaches have been employed, all of which have disadvantages.
Several approaches involve merely instituting employee procedures. For example, all operations in an upper level are stopped while another worker is in the lower level (sub fab) area, or areas in the lower level below which chemical dispensing and possible spills may occur are chained off and contain "dangerous area" warning signs. If access to the "dangerous area" is required, hazardous work permits are issued and appropriate safety apparel, such as chemical resistant clothing, goggles, face shields, gloves, and the like would be worn when personnel access the area. While not causing an interruption in airflow, such procedures in addressing spill problems are inefficient, cumbersome and subject to human error.
Another approach is to install chemical resistant "umbrellas" on or over critical equipment in the lower level sub fab area and have personnel routinely wear appropriate safety apparel. "Spill pans" might also be located under equipment in the upper level. Such umbrellas and spill pans would typically need to be associated with each piece of equipment involved and would be costly additions to the equipment, particularly where chemical resistant materials are needed. Such umbrellas would not effectively protect personnel unless routinely carried by the workers in the lower level areas. In addition, such spill pans and umbrellas can adversely affect the uniform airflow.
Another technique involves installing a large container, or series of small containers packed close together, below the open flooring and spanning the entire room to capture any spills, or funnel spills into a adjacent receptacle(s) in the room below. However, again, such a large container or series of containers would interfere with the needed uniform airflow.
Another approach to spill containment is described in U.S. Pat. No. 5,180,331 titled "Subfloor Damper and Spill Container" issued to Daw et al where a spill container system is employed below open flooring. However, while the Daw approach captures spills and recognizes the need to maintain airflow, the Daw approach adds additional mechanical structural complexity to adjust for airflow interference created by its various embodiments. In addition, the size relationships of various elements used to practice the Daw invention do not optimize the amount of spill capture for a given pressure loss.
While the prior approaches may deal with solving spill containment, most do not address the need for simultaneous spill containment and airflow continuity. Where both are addressed (as in the Daw approach), complexities are added. What is needed is a simple, cost effective, easy to use and install, efficient approach for simultaneously addressing spill containment and uniform airflow. The invention as described herein provides such an approach.